Rheostat



I 1,618,801 Feb. 22, 1927- BOHLMAN RHEOSTAT Filed Oct. 23, 1922 PatentedFeb. 22, 192 7.

UNITED STATES PATENT OFFICE.

ERNEST A. BOIILMAN, or CHICAGO, ILLINOIS, ASSIGNOR T KELLOGG swrrcnnomAND SUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

RHEOSTAT.

Application filed October 23, 1922. Serial No. 598,316.

My invention relates to rheostats, such as are used for controlling thefilaments of electron tubes, and has to do more particularly with animproved rheostat in which the resistance element is rotated.

A feature of my invention lies in the provision of a resistance coilmounting unit so constructed that the heating of the resistance elementor coil is greatly reduced, and also simplified means for securing theresistance element or coil to said mounting unit.

Another feature relates to the construction of the insulated disk thatcarries the resistance element, the means for holding the resistanceelement in place and the construction of the contact springs forcooperation with the resistance element.

Other features of my invention reside in the details of constructionwhich produce a very eflicient, easily operated, but economical toconstruct device.

The above features, as well as others, will be pointed out more indetail in the ensuing specification, and for a clearer understanding ofmy invention reference may be had to the drawing, in which likereference characters denote like parts in the several views, and inwhich- Fig. 1 is a front plan view of my rheostat in its normalposition;

Fig. 2 is a left side view of Fig. 1;

Fig. 3 is a sectional view of my rheostat along the line 11 of Fig. 1;

gig. 4 is a back plan view of my rheostat; an

Fig. 5 is a sectional view showing the mounting unit and the means forsecuring the resistance element or coil on said mounting unit.

Referring now more articularly to my invention, 2 is a round at piece ofnon-conducting material having an extension 3 integrally formedtherewith, and also provided with a plurality of peripheral slots 4 forreceiving holding clips 5. A pair of nonconductor disk members 10 and11, larger in diameter than the diameter of the member 2, are providedand which are adapted to be secured to the sides of the member 2, bymeans of suitable rivets 12. A resistance element or coil 6 is providedwhich is slightly formed lugs 9 on each side thereof, said other endadapted to fit in the peripheral slot 4 of the member 2 and the lu s 9extend outwardly beyond the sides Of t e member 2. In assembling thevarious parts mentioned above, the end of the clips 5 carrying the lugs9 is fitted into the peripheral slots 4 1n the member 2. The diskmembers 10 and 11 are provided with openings 13 for receivmg the lugs 9of the clips 5, and are socured to the member 2 by suitable rivets 12.The resistance element or coil 6 has the lower portion of a few of itsturns 8 at difi'erent places engaging the turned over ends 7 of theclips 5, and since the diameter of the turns 8 of the coil 6 is greaterthan the thickness of the member 2, the coil 6 rests upon and betweenthe inner edges of the disk members 10 and 11, said coil being drawntaut and secured in this position by the clips 5, the ends of the coil 6being separated from each other by the extension 3 of the member 2, saidextension 3 having extending portions 3 which engage the upper portionof the turns 8 at the ends of the coil 6 to prevent the said ends fromflarin up. By having the coil 6 resting upon t e inner edges of themembers 10 and 11, an air space is provided between the coil 6 andmember 2,

which will permit thecirculation of air to reduce the heating of thecoil 6. The members 10 and 11 engaging the lugs 9 of the clips 5 securesaid clips in place in the slots 4, and the rivets 12 secure the members2, 10 and 11 together as a single unit.

A cylindrical member 15 of conducting material is provided, which has anintermediate reduced portion 16 and a further reduced end portion 17,said member 15 adapted to extend through a central orifice 18 in themembers 2, 10 and 11 until the intermediate portion 15 engages thecentral orifice 18, the orifice 18 being slightly smaller in diameterthan the diameter of the reduced portion 16, so that a drive fit iseffected. A plate 19 of conducting material having a suitable opening inits one end for receiving the reduced portion 16 of the member 15, isprovided and clamped between the members 10 and 15, the other end ofsaid plate 19 having an orifice for receiving one end of the coil 6,whereby said plate connects the coil 6 with the member 15. A flat washer20 having a. suitable opening fits over the reduced portion 16 extendingthrough the central opening 18 in the members-2, 10 and 11,

' and engages the face of the member 11. The

end of the reduced portion 16 is now pierced or blunted at severalplaces by a punching operation to prevent the dlsplacement of the washer20, whereby the member 15 1s securedly held in the central openrng 1801the members 2, 10 and 11. A stop p111 21 1s provided and is secured insuitable opemngs 1n the members 2 and 10 by means of a drive fit, andthe purpose of said stop pin 21 Will be pointed out later.

A pair of contact wipers 23 for engaging the resistance element or coil6 are provlded which are separated from each other and secured to aterminal member 26, and between a pair of mounting legs 24 but lnsulatedtherefrom by non-conducting members 25 by means of suitable screws 126which extend through suitable openings 1n the -legs 24, terminal member26, insulated members 25, and have screw-threaded engagement withsuitable tapped orifices in another terminal member 27 which terminalmember 27 is in contactual engagement with one of the mounting legs 24.A shaft or rod 28 of conducting material having a thumb and finger knob29 of insulating material secured to its one end by a screw-threadedengagement is provided, there being a fiat washer 30 for engaging thethreaded end portion of said shaft or rod 28, and which also en ages theinner face of the knob 29. Secure to the terminal members 26 and 2'2 bymeans of screws 31 and 32 are term nals 33 and 34, respectively, whichtermlnals 33 and 34 are adapted to have conductors connected to them forpurposes well known to those skilled in the art.

The manner in which the resistance element or coil is secured inoperative relation with the stationary contact wipers 23 will now bedescribed. The resistance coil carrying unit is inserted between themounting le s 24 and the extension 3 of the member 2 is inserted betweenthe contact wipers 23, said contact wipers having a spring effectwhereby they tend to s ring together to grip the extension 3. The shaftor rod 28 is now inserted into and through suitable openings in the legs24 and through the central opening 16 in the member 15, the legs 24engaging the ends of said member 15 to prevent endwise movement of saidmember 15. A set screw 37 is rovided in the member 15 and when the s aftor rod is extended through the member 15 and the legs 24, said set screw37 is caused to engage the shaft or rod 28, thereby causing the coilcarrying unit and shaft 28 to rotate together when the knob 29 isturned, and to also prevent the removal of the shaft 28. A stop pin 38is suitably secured to on of the legs 24 and in the path of travel ofthe pin 21 for limiting the extent of rotation of the coil In Figs. 2and 3 I show a mounting member 40 to which my rheostat may be mounted inany suitable manner, the shaft or rod 28 being first extended through asuitable opening in said mounting member until the outer face of thewasher 30 engages the face of the mountin member. By having the shaft orrod adjusted in the legs 24 and member 15 of my rheostat by means of theset screw 37, it is at once apparent that my rheostat may be mounted onmounting members of different thicknesses.

Having described a particular structure of my invention it is to beunderstood that I do not wish to be limited to the exact structure asdescribed and illustrated, but I wish to cover all that comes within thescope and spirit of the appended claims.

Having described my invention what I claim as new and desire to secureby Letters Patent is:

1. In a rheostat including a resistance element, a supporting unitcomprising three plates secured together and adapted to have saidresistance element secured thereon, but only in contactual engagementwith two of said plates, clips secured to said supporting unit forretaining said resistance element on said supporting unit, contactwipers, and means for rotatably associating said resistance element withsaid contact W1 ers.

2. In a device of the class describe including a resistance coil, aresistance coil carrying unit, said resistance coil carrying unitcomprising a disk member having a disk member secured to each sidethereof and adapted to receive said resistance coil in such manner thatsaid resistance coil does not engage said first disk member, holdingclips for retaining said resistance coil on said unit, supporting meanshaving contact members secured thereto, and means for rotatablysupporting said unit on said supporting means and to effect theengagement of said resistance coil and said contact members.

3. In a rheostat including a resistance element, supporting means forsaid resistance element comprising three plates of non-conductingmaterial secured together, a clip engaging a slot in one of said latesand having integrally formed lugs or engaging said other two plates toprevent the displacement of said clip, said clip engaging the resistanceelement to retain the same in its mounted position on said supportingmeans, a mounting frame having stationary contact wipers securedthereto, and means for rotatabl supporting said supporting means on saiframe and the resistance element in operative relation with said contactwipers.

4. In a device of the class described including a round fiat piece ofnon-conducting material provided with a plurality of peripheral slots,clips for engaging said slots, a disk member, greater in diameter thanthat of said flat piece, secured to each side of said fiat piece to forma single unit 1, said disk members engaging said clips to prevent theirdisplacement from their respective slots, a resistance coil adapted toengage the inner edges of said disk members and secured thereto by saidclips, a pair of mounting legs having a pair of contact wipers securedthereto, and means for rotatably supporting the coil carrying unitbetween said mounting legs and said resistance coil in operativerelation with said contact wipers.

5. In a rheostat as described including three disks of non-conductingmaterial secured together to form a unit, one of said disk members beingsmaller in diameter than the diameter of said other disks andsecuredbetween said other disks to provide an opening between the peripheraledges of said other disk members, a resistance element adapted to engagesaid opening and to engage the inner edges of said other disk members,without engaging the central disk member, holding clips secured in saidcentral disk members for retaining said resistance element in itsmounted position,

mounting means having a pair of contact members secured thereto, andmeans for rotatably associating said resistance element with said pairof contact members.

6." In a rheostat including a resistance element, a unit comprisingthree flat disk members secured together for supporting said resistanceelement, said resistance element engaging only two of said disk memberswhile an air gap is provided between said resistance element and theother of said disk members, means for holding said resistance element inits supported position, said means engaging slots in said other diskmember and held therein by said two disk, members, mounting means havingcontact members secured thereto, and means for supporting said unit onsaid mounting means to bring said resistance element in operativerelation with said contact members.

7. In a device of the character described includin a non-conductingmember provided--w1tha plurality of peripheral slots, a clip forengaging each of said slots, a pair of disk members greater in' diameterthan the diameter of said first member and secured to said first member,said disk members engaging the clips -to prevent. their reframe, contactmembers secured to said sup-' porting f "ame, and means for rotatablysupporting said first member and said disk members on said supportingframe, to bring said resistance element in operative relation with saidcontact members, said means being mlcrometrically adjustable to permitsaid device to be secured tomounting members of different thicknesses.

8. In a rheostat including a resistance coil, means for supporting saidresistance coil, said means con'iprising three plates secured togetherso that said re istance coil-only engages two of said plates, the thirdplate provided with an integrally formed extension for separating theends of said coil and for retaining said ends in their supportedposition, clips engaging said means and adapted to engage theconvolutions of said resistance coil to maintain said resistance coil inits supported position, mounting means having contact members securedthereto, and means for rotatably supporting said coil supporting meanson said mounting means and to operatively associate said-resistanceelement with said contact members,

aid contact members adapted to engage the extension on said third platewhen the rheostat is in its normal position, but to disengage saidextension and to engage said resistance element when in its operatedposition.

9. In a rheostat including a terminal member, a contact member securedto each side of said terminal member and in contact-ual engagement. withsaid terminal mem ber, said contact members extending substantiallyopposite each other, a mounting leg secured to each side of saidterminal member but insulated from said contact members, said contactmembers extending between said legs, a resistance coil, mounting meanscomprising three plates and adapted to have said resistance coil mountedthereon, one of said plates having an integrally formed extension forseparating the ends of said coil and for retaining said ends in positionon said mounting means, a micrometrically, adjustable shaft forrotatably supporting said mounting means and resistance coil betweensaid mounting legs so that said contact members engage said extensionwhen said rheostat is in normal position and to engage said resistancecoil when said rheostat is in ofi normal position.

10. In a rheostat including a terminal member, a. pair of contactmembers secured to said terminal member and separated from each other bysaid terminal member, a mounting leg secured'to each side of saidterminal member but insulated from said contact members, said contactmembers extending between said mounting legs, a resistance coil, aresistance coil carrying unit adapted to have said resistance coilsecured thereon, said unit comprising three plates one of said plateshaving an integrally formed extension for breaking the circuit of saidresistance coil and for maintaining the ends of said coil in positiononsaid unit, means for supporting said unit between said mounting legsand said resistance coil in operative relation with said contactmembers, said contact members having a spring effect and of suflicientlength to insure contactual engagement with said resistance coil whensaid rheostat is in its operated position and to disengage saidresistance coil and to engage said extension when in its normalposition.

11. A rheostat including a resistance w re, a supporting unit consistingof a plurality of elements, two of whichcontact with the wire, andholding means spaced on another of said elements and supported therebyfor securing the resistance wire in place, said last element beingsubstantially smaller in diameter than said other two elements andlocated between said two elements to form a receptacle for saidresistance wire and to provide an air gap between said third element andthe resistance wire.

12. A device of the character described including a mounting frame, aresistance element, a air of contacts secured to said mounting rame,means including a plurality of disks, one of said disks being smaller indiameter and located between two other disks to form a receptacle forthe resistance element and to provide an air gap between said first diskand said element, for rotatably supporting said resistance element onsaid mounting frame and in operative relation with said pair ofcontacts, said element resting in engagement with two of said disks, andmeans supported by, another of said disks for maintaining said elementin position against movement.

13. A device of the class described including a pair of contacts, aresistance ele ment, members secured together to form a unit, saidmembers including three disks, one of which is smaller in diameter andlocated between the other disks to form a receptacle for said resistanceelement and to provide an air gap between said element and said firstdisk, said resistance element secured to said unit and engaging only twoof said members, holding means secured to another of said members formaintaining said element in engagement with said two members againstmovement, and means for rotatably supporting said unit and saidresistance element inoperative relation with said pair of contacts.

14. A device of the character described includinga plurality of platessecured together to form a single unit, a resistance element engagingonly a pair of plates 01': said unit, one of said plates being smallerin diameter and located between the other plates to form a receptaclefor the resistance element and to provide an air gap between the saidelement and center plate, 9, lug integrally formed with one of saidplates, spring contacts, and means for rotatably securing saidresistance element and unit in operative relation with said springcontacts, said spring contacts adapted to engage said resistance elementto close a circuit therethrough, and adapted to enga e said lug to .openthe circuit through said resistance element. 15. A device of the classdescribed including a resistance element, a circular plate unitconsisting of three plates one of which is smaller in diameter than theother two and is located between said other two to form a receptacle forthe said resistance element and to provide an air gap between saidelement and said center disk, means for securing said resistance elementto said plate unit, an extending portion for said plate unit, and'meansfor rotatably supporting said plate unit and resistance element, andspring contacts for engaging said resistance element to close a circuitand to engage said extending portion to open said circuit.

16. A device of the character described in- ,cluding a mounting frame, acircular plate unit, a resistance element, means for securing saidresistance element to said unit, said plate unit comprising threeplates, one of said plates being smaller in diameter than the otherplates and located between said other plates to separate the same toform a. recess for the resistance element and to provide an air gapbetween the said element and center plate, an extension integrallyformed with one of the plates of said unit, contacts secured to saidmounting frame, means for rotatably supporting said unit and resistanceelement in operative relation with said contacts, said contacts engagingsaid resistance element to close a circuit and to engage said extensionto open said circuit, and stop pins for limiting the degree of rotationof said resistance carrying unit.

Signed by me at Chicago, in the county of Cook and State of Illinois,this 19th day of October, 1922.

ERNEST A. BOHLMAN.

